Composts hold water and keep soil aerated; some provide nutrients.
Pure sphagnum moss peat composts from Ireland, England, U.S. and elsewhere are best for seeding and potting.
They are clean, light, easy to handle, highly absorbent, moderately acid, porous, and sterile.
They provide very little plant food, so plant-specific nutrients can be added.
Original British "John Innes" style soil-based composts consist primarily of sphagnum moss peat and high quality loam.
Low quality brands contain too little humus and become impervious to air and water.
Multi-purpose non-soil peat composts were developed as high quality loam became scarce.
Some contain chemicals and wetting agents.
Multi-purpose non-peat composts were developed as high-quality peat became scarce, initially using non-toxic softwood bark from timber waste.
Many commercial composts use recycled materials.
Dehydrated and limed sewer sludge is mixed and oxidized with bark sawdust, as well as organic household waste and plant waste.
Some commercial composts add chemical nitrogen or animal waste.
Home gardening composts can be any garden (leaves, grass) or kitchen refuse (fruits, vegetables, husks, egg shells, coffee grounds, canning waste, not meat), on top of twigs or chopped corn stalks to aid aeration and drainage.
Top with grass clippings or manure (20%).
Keep moist and stir monthly to aerate.
Cover loosely to retain heat.
In apartments use a plastic bag, but aerate frequently.
Composting kits add helpful organic compounds.
Compost can also be used as top-cover mulch to hold in moisture.
Fungus composted wood chips are used to decontaminate organic compounds from soil.
